Stack sensing sheet feed conveyor control means

ABSTRACT

A stop plate is provided against which the forward edge of sheets discharged from a conveyor to form a stack impinge with a photoelectric cell being mounted in the stop plate for sensing the top of the stack to actuate a drive motor for sequentially lifting the discharge end of the conveyor as the height of the stack progresses.

United States Patent Lucas [54] STACK SENSING SHEET FEED CONVEYOR CONTROL MEANS [72] Inventor: Raymond L. R. Lucas, Avenue de La Republique, Prechac, Gironde, France [22] Filed: April 29, 1970 [21] Appl.No.: 32,861

52 user. ....2s0 222R, 271/68 51 lnt.Cl. ..G06m 7/00 [58] Field of Search ..250/239, 221, 222, 234; 271/68 [56] References Cited UNITED STATES PATENTS 3,226,703 12/1965 Finkle ..250/239 June 20, 1972 Basehore et a1. ..250/239 Konrad et a1.

3,483,507 12/ l 969 Griswold 250/239 2,894,147 7/1959 Stidwill .250/234 3,030,107 4/1962 Stidwill ..271/68 Primary Examiner-Walter Stolwein Att0rne vMason, Fenwick & Lawrence ABSTRACT A stop plate is provided against which the forward edge of sheets discharged from a conveyor to form a stack impinge with a photoelectric cell being mounted in the stop plate for sensing the top of the stack to actuate a drive motor for sequentially lifting the discharge end of the conveyor as the height of the stack progresses.

10 Claims, 5 Drawing Figures STACK SENSING SHEET FEED CONVEYOR CONTROL MEANS The subject invention is in the field of sheet stackers and is specifically directed to electronic means for sensing the stack height for the control of a conveyor feeding sheets to the stack.

Previously known stackers have been employed for the purpose of conveying planar members such as cardboard sheets from the outlet of a processing machine such as a slotter, cutter, printing press or the like by sheet conveyor means which have a discharge end that is progressively lifted upwardly as the stack height increases. A stop or gauge plate is nonnally provided forwardly of the discharge end of the sheet conveyor so that the sheets discharged from the conveyor engage the stop plate on their forward edge and are positioned in a substantially vertical array.

Previously, the upward movement of the discharge end of the conveyor has been controlled in several different ways.

'For example, electrical sensor means in the form of photoelectric cells, microswitches and other devices have been positioned forwardly of the stop plate for detecting the formation of a stack of a given desired height or the passage of individual sheets to actuate motor means for providing for incremential upward movement of the conveyor discharge end. Switch activating arms have been mounted adjacent the stop plate for this purpose; however, the continuing impingement of discharged sheets against such switch arms eventually results in malfunction of such switches and weakening of the spring means normally employed for maintaining such switches in an open condition. Electric eye sensor means which have also been employed in prior devices are difficult to adjust and are subject to malfunction by the collection of dirt or dust in the sensor or the light source or reflector and are also subject to being erroneously activated by virtue of the passage of a hand of the operator in front of the beam or by a deflected sheet or the like passing in front of the beam. Additionally, some of the prior known photoelectric sensing devices must be cyclically desensitized and timed so that the continuous passage of sheets in front of the eye does not produce a continuous response for operating the lifting motor for pivotally moving the discharge end of the sheet conveyor upwardly as the stack progresses.

Avoidance of the major disadvantages of the prior known systems for controlling the lifting movement of the discharge end of the conveyor is enabled by the subject invention through the provision of a photo-resistant electric cell or a photodiode cell mounted flush with the sheet impingement surface of the stop plate. Consequently, there is no projection beyond the plane of the plate and the cell is not engaged by the sheets discharged from the discharge end of the conveyor. The photo-resistant electric cell is connected to a conventional relay and a power amplifier which serves to control an electric motor operable for vertically moving the discharge end of the conveyor a set predetermined increment.

Another significant characteristic of the present invention resides in the fact that the photo-resistant electric cell or photodiode is mounted in the stop plate and is fully protected while being easily removable for servicing. Another significant characteristic of the subject invention resides in the fact that the electric cell is of less thickness than the marginal plate and the receiving plane of the cell is parallel to the face of the stop late. p Yet another advantage of the subject invention is that it substantially reduces the initial cost of the sheet control mechanism and is also economically advantageous in providing a reliable and trouble-free operation.

Since the photoelectric cell and the discharge end of the conveyor are all supported for vertical movement as a unit, detection of the top of the stack (by the blockage of ambient light to the cell)causes the cell to actuate the control motor for lifting the discharge end of the conveyor, the stop plate and the cell mounted thereon a given amount wherein the cell is not obstructed by the stack. The cell by means of its relay and power amplifier circuit controls the lifting movement of the discharge end of the conveyor and this movement also serves to reposition the cell for the next cycle of operation. The system continues to cycle in this manner until the pile has reached its desired height.

A full understanding of the preferred embodiment of the subject invention will be better understood with reference to the drawings in which:

FIG. 1 is a side elevational view of the movable discharge head of a conveyor and stack having a conventional photoelectrical cell sensing device;

FIG. 2 is a side elevational view of another stop plate equipped with conventional mechanical switch operating sensing means;

FIG. 3 is a perspective view of a photo-resistant electric sensing cell employed in the subject invention;

FIG. 4 is a enlarged view of a portion of a stop plate of the preferred embodiment in which the photo-resistant sensing cell of FIG. 3 is mounted; and

FIG. 5 is a sectional view taken along lines 5-5 of FIG. 4.

Turning first to FIG. 1, it should be noted that a conventional pivotal conveyor support frame 1 is shown with it being understood that there is another identical frame member on the opposite side of the device with a shaft 2 being provided to extend between the two frame members. A roller 3 is supported by shaft 2 and a conventional conveyor belt 4 extends about the periphery of the roller for feeding cardboard or the like sheets 5 along its upper flight in the direction indicated by arrow F in a conventional manner for deposit on stack S. Additionally, a movable support arm 6 is pivotally connected to the shaft 2 on each end of the shaft for providing support for a horizontally extending stop plate support arm 7 extending forwardly from the discharge end of the conveyor. The stop plate support arm 7 is maintained in a horizontal position by virtue of a brace member 9 connected to the support arm 6. Support arm 7 is always maintained in a horizontal position by virtue of a connecting parallelogram linkage including elements 1,6,9 and the main frame of the machine (not shown). Such a conventional linkage is illustrated in my prior filed application Ser. No. 743,419, now US. Pat. No. 3,549,l44.

In the prior known system of FIG. 1, a conventional photoelectric cell 10 is mounted on a projection forwardly of the roller 3. FIG. 2 illustrates a conventional electric sensor 11 mounted on the stop 8 for detecting sheets fed to the top of the stack S as they arrive in contact with the sensing means.

Actuation of the photoelectric cell 10 of FIG. 1 or the switch arm 11 of FIG. 2 serves to initiate operation of a motor for incrementially moving the discharge end of conveyor 1 etc. upwardly through a desired increment of movement.

A portion of the preferred embodiment of the subject invention is illustrated in FIG. 3 and comprises a photo-resistant electric cell 12 having leads 13 and 13a. FIG. 4 illustrates the manner in which the photo-resistant electric cell 12 is mounted in a modified stop plate 8'. The photo-resistant electric cell 12 is mounted in substantially horizontal alignment with the discharge end of the conveyor 1 etc. and wires 14 and 14a are connected to leads 13 and 13a and extend upwardly in a vertical groove formed in the modified stop plate 8' for connection to a conventional control circuit. The control circuit controls the conveyor lifting motor which, when actuated for a cycle of operation, causes the motor to operate to move the conveyor upwardly in a increment of movement.

The photo-resistant electric cell 12 is positioned behind a transparent plate 15 which covers the vertical groove in which the cell 12 is positioned and which holds the cell in position in the stop plate 8'. A wedge and adjustment lining member 17 is provided to the rear of the cell 12 as is best shown in FIG. 5. A metallic plate 18 is mounted immediately above the transparent plastic plate 15 and covers the remainder of the vertical slot in which cell 12 is mounted. Retention of the transparent plate 15 and the metal plate 18 in the modified stop plate 8' is enabled by the provision of a plurality of screws 19.

The cell 12 is positioned so that the movement of the stack upwardly eventually covers the cell to provide a readout signal to the control circuit (not shown) for initiating a cycle of operation of the motor for lifting the discharge end of conveyor 1, etc. Cell 12 is responsive to the blocking of the environmental light by the top of the stack for providing the motor actuating signal. However, if the device should be employed in a dark location, the environmental light may not be adequate and it may be necessary to mount a light beam source adjacent the end of the conveyor for directing a light beam into the sensor.

It should be understood that the subject invention is susceptible to other modifications which will be obvious to those skilled in the art. For example, the wires 14 and 14a could be extended immediately rearwardly of the sensor 12 to eliminate the upper portion of the vertical slot in which the sensor is positioned. Moreover, a plurality of photo-resistant cells could also be mounted in the stop plate 8' if such should be desired.

Many other modifications and variations will occur to those skilled in the art; therefore, it should be understood that the subject invention should be limited solely by the appended claims.

I claim:

1. In a sheet stacker of the type employing a discharge conveyor having a discharge end movable in a vertical plane from a lower position to an upper position by electric motor means and having a stop plate supported adjacent the discharge end of the conveyor by means connected to the conveyor for vertical movement with the discharge end of the conveyor for engagement by the forward edges of sheets discharged from said conveyor, the improvement comprising a photo-resistant electric cell mounted in said stop plate in the plane of abutment of the stop plate and means connecting said photo-resistant cell to the control means of said motor for actuating said motor to initiate an increment of movement of the discharge end of said conveyor for lifting the discharge end of said conveyor an increment of movement in response to the top of said stack extending in blocking relationship to said photo-resistant cell.

2. The invention of claim 1 wherein said photo-resistant electric cell is mounted in the thickness of said stop plate and is flush with the abutment plane of said stop plate facing said conveyor against which plane the forward edge of sheets discharged from said conveyor strike and wherein there are no projections from the abutment plane of said stop plate capable of deflecting the discharged sheets fed against said stop plate.

3. The invention of claim 2 wherein said photo-resistant cell is mounted in a slot formed in said stop plate and is protected by a sheet of transparent plastic material arranged flush with the plane of said stop plate immediately in front of said cell.

4. The invention of claim 1 wherein said photo-resistant electric cell is in substantially horizontal alignment with the discharge end of said discharge conveyor.

5. The invention of claim 4 wherein said photo-resistant electric cell is mounted in the thickness of said stop plate and is flush with the abutment plane of said stop plate facing said conveyor against which plane the forward edge of sheets discharged from said conveyor strike and wherein there are no projections from the abutment plane of said stop plate capable of deflecting the discharged sheets fed against said stop plate.

6. The invention of claim 5 wherein said photo-resistant cell is mounted in a slot formed in said stop plate and is protected by a sheet of transparent plastic material arranged flush with the plane of said stop plate immediately in front of said cell.

7. The invention of claim 6 wherein said slot is a vertically extending slot.

8. The invention of claim 7 additionally including a metallic plate mounted immediately above said sheet of transparent plastic material and covering all portions of said vertically extending slot not covered by said sheet of transparent plastic material.

9. The invention of claim 1 wherein said photo-resistant electric cell is mounted in a vertical slot in the thickness of said stop plate and is flush with the abutment plane of said stop plate facing said conveyor against which abutment plane the forward edge of sheets discharged from said conveyor strike and wherein there are no projections from said abutment plane of said stop plate capable of deflecting the discharged sheets fed against said stop plate.

10. The invention of claim 9 additionally including a sheet of transparent material arranged flush with the abutment plane of said stop plate immediately in front of said photo-resistant cell. 

1. In a sheet stacker of the type employing a discharge conveyor having a discharge end movable in a vertical plane from a lower position to an upper position by electric motor means and having a stop plate supported adjacent the discharge end of the conveyor by means connected to the conveyor for vertical movement with the discharge end of the conveyor for engagement by the forward edges of sheets discharged from said conveyor, the improvement comprising a photo-resistant electric cell mounted in said stop plate in the plane of abutment of the stop plate and means connecting said photo-resistant cell to the control means of said motor for actuating said motor to initiate an increment of movement of the discharge end of said conveyor for lifting the discharge end of said conveyor an increment of movement in response to the top of said stack extending in blocking relationship to said photo-resistant cell.
 2. The invention of claim 1 wherein said photo-resistant electric cell is mounted in the thickness of said stop plate and is flush with the abutment plane of said stop plate facing said conveyor against which plane the forward edge of sheets discharged from said conveyor strike and wherein there are no projections from the abutment plane of said stop plate capable of deflecting the discharged sheets fed against said stop plate.
 3. The invention of claim 2 wherein said photo-resistant Cell is mounted in a slot formed in said stop plate and is protected by a sheet of transparent plastic material arranged flush with the plane of said stop plate immediately in front of said cell.
 4. The invention of claim 1 wherein said photo-resistant electric cell is in substantially horizontal alignment with the discharge end of said discharge conveyor.
 5. The invention of claim 4 wherein said photo-resistant electric cell is mounted in the thickness of said stop plate and is flush with the abutment plane of said stop plate facing said conveyor against which plane the forward edge of sheets discharged from said conveyor strike and wherein there are no projections from the abutment plane of said stop plate capable of deflecting the discharged sheets fed against said stop plate.
 6. The invention of claim 5 wherein said photo-resistant cell is mounted in a slot formed in said stop plate and is protected by a sheet of transparent plastic material arranged flush with the plane of said stop plate immediately in front of said cell.
 7. The invention of claim 6 wherein said slot is a vertically extending slot.
 8. The invention of claim 7 additionally including a metallic plate mounted immediately above said sheet of transparent plastic material and covering all portions of said vertically extending slot not covered by said sheet of transparent plastic material.
 9. The invention of claim 1 wherein said photo-resistant electric cell is mounted in a vertical slot in the thickness of said stop plate and is flush with the abutment plane of said stop plate facing said conveyor against which abutment plane the forward edge of sheets discharged from said conveyor strike and wherein there are no projections from said abutment plane of said stop plate capable of deflecting the discharged sheets fed against said stop plate.
 10. The invention of claim 9 additionally including a sheet of transparent material arranged flush with the abutment plane of said stop plate immediately in front of said photo-resistant cell. 